Frequency converter with fan cooling

ABSTRACT

The invention relates to an air-cooled frequency converter, especially for construction site equipment, such as internal and external vibrators which are operated at a higher frequency than the existing electricity supply, said frequency converter comprising a housing and preferably being connected to a separation transformer for producing a protective extra-low voltage. Said housing is divided into two sections, that is into a converter receiving element surrounding a plate chamber, and a housing section connected to said receiving element and used as a cooling region, inside which cooling air channels and a fan for conveying the cooling air through the cooling air channels are arranged. The configuration of the housing in the cooling region and optionally the embodiment of a transformer chamber are created by annular profiled elements which are cross-cut as desired, surround each other in an interspaced manner, and are coaxially arranged in relation to each other.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a frequency converter according to thepreamble of Claim 1, in particular for devices used at constructionsites.

2. Description of the Related Art

At construction sites, as a rule the power supplied is line currenthaving a frequency of 50 Hz and a voltage of 230 V (sometimes also 400V). The frequency converter to which the present invention relatesconverts this power available at the site into, for example, athree-phase current having a frequency of 200 Hz and a protectiveextra-low voltage of 42 V, the protective extra-low voltage beingrequired in order to protect the operator from electrical risk, e.g. ina wet environment.

In known devices of this type, an isolating transformer and a convertercircuit board are used that, due to their power loss, release heat thathas to be dissipated. This is achieved through the use of heat sinkshaving a sufficiently large cooling surface, a sufficiently largehousing, or overdimensioning of the isolating transformer. These heatdissipation measures are cost-intensive and result in greater weight.The known devices can have external cooling fins that can accumulatedirt and concrete over time, which has an increasingly adverse effect onthe heat dissipation.

From EP-A-0 854 565, a frequency converter is known that has a converterdevice surrounded by a housing for converting an electrical currentfrequency. The housing has a converter receptacle that surrounds a boardchamber for the converter device, as well as a housing segment,connected to the converter receptacle, that acts as a cooling area,inside which there are situated cooling air ducts and a fan suited forconveying cooling air through the cooling air ducts.

OBJECTS AND SUMMARY OF THE INVENTION

The object of the present invention is therefore to design an air-cooledfrequency converter of the type indicated above in such a way that theconstructively determined cooling efficiency is maintained even over alonger period of use, while also enabling a smaller, more compactconstruction so that weight and manufacturing costs are reduced, andalso such that, as a further cost-reducing measure, a predeterminedbasic construction can be used for devices of different power classes.

In order to achieve this object, according to the characterizing part ofClaim 1 the present invention is characterized in that the housing has aconverter receptacle that surrounds a board chamber for the converterdevice, and a housing segment that is connected to the converterreceptacle and that acts as a cooling area in whose interior there aresituated cooling air ducts and a fan that is suitable for conveyingcooling air through the cooling air ducts, and in the cooling area thehousing has an external first annular or extruded profile, in relationto whose axis additional annular extruded profiles are oriented to oneanother in such a way that they surround each other so as to formannular chambers at a distance from one another, transverse to the axialdirection, and the annular or extruded profiles situated within thefirst extruded profile end with an axial spacing from the converterreceptacle so as to form an air deflection.

The construction according to the present invention combines the housingand the cooling system to form a compact unit in which the active aircooling by the fan or ventilator enables the reduction of the requiredcooling surfaces, and in which external cooling fins, which are liableto dirtying and thus to reduction of cooling efficiency, can be omitted.

In an advantageous further development of the present invention, thecooling area has a transformer chamber, adjacent to the cooling airducts, that accommodates an isolating transformer for producing anoutput voltage that differs from a line voltage. In this way, theisolating transformer and the converter device can be combined to form aunit as a frequency converter, the isolating transformer being situatedin the cooling area itself for optimal cooling. The isolatingtransformer can be used to produce a protective extra-low voltage, e.g.42 V. Of course, it is also possible to use the isolating transformer toproduce an output voltage having a higher value than the line voltage.

In a particularly advantageous construction, within the first extrudeprofile, and coaxial thereto the fan is situated in the air deflectionbetween the additional extruded profiles and the converter receptacle soas to be suitable for suctioning a cooling air stream via one of theannular chambers and expelling this stream via a different annularchamber according to the counterflow principle.

The use of extruded profiles as annular profiles enables a particularlysimple, economical, and highly compact construction of the device. In avery useful development, the extruded profile adjacent to the firstextruded profile can enclose an annular transformer chamber that islimited inwardly by a third extruded profile. The transformer chamberpreferably contains a toroidal core transformer assembly.

According to a particularly useful specific embodiment, the extrudedprofiles are aluminum extruded profiles that have been cut to fit.Depending on the dimensioning of the isolating transformer, theconstructive shape of the housing in the cooling area can be adapted tothe space requirement of the transformer through a suitable selection ofthe length of the extruded profiles.

In a further very advantageous construction, the third annular orextruded profile is made up of an external and an internal ring so as toform a heat sink, cooling fins being situated in the area between theouter and the inner ring, forming one of the cooling air ducts togetherwith the outer and inner ring.

A very simple installation is enabled in that according to a preferredfeature the outer, first extruded profile engages with the adjacentextruded profile according to the tongue and groove principle.

Further advantageous and useful constructions of the present inventionresult from the following description of an exemplary embodiment inconnection with the subclaims.

The present invention is explained in more detail on the basis of theexemplary embodiment of the present invention shown in the Figures, inthe form of a frequency converter having an isolating transformer forproducing a protective extra-low voltage and circulated air cooling.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a perspective side view of the device according to thepresent invention made up of a protective carriage and the device body,

FIG. 2 shows a view in the direction of arrow II in FIG. 1, in asomewhat larger scale,

FIG. 3 shows a longitudinal section through the device along the lineIII-III in FIG. 2, in a further enlarged scale,

FIG. 4 shows a representation, similar to that in FIG. 3, of theinstalled housing of the device body without the converter board and theisolating transformer,

FIG. 5 shows a perspective view of the basic body,

FIG. 6 shows a cross-section through the external annular profile thatforms the housing segment that accommodates the transformer,

FIG. 7 shows a cross-section through the basic body profile that formsthe air guide, and

FIG. 8 shows a cross-section through the extruded profile that forms theheat sink.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A frequency converter according to the present invention has a converterdevice for converting the electrical current frequency from a linefrequency to an electrical current having a higher frequency. Inaddition, as a component of the frequency converter an isolatingtransformer is provided with which the line voltage of for example 230 Vor 400 V is transformed into a lower voltage, e.g. 42 V, so that theperson working with the frequency converter or a construction deviceconnected thereto, such as e.g. an internal vibrator for compactingconcrete, will not be endangered by high electrical voltages.

As FIG. 1 shows, the device according to the present invention is madeup of the actual device body 10, which contains the electrical equipmentand peripheral equipment, and a frame-type protective carriage 12 thatshields device body 10 on all sides and with which device body 10 isconnected in releasable fashion via a plurality of connection points.

As is shown in FIGS. 2 to 5, device body 10 has an essentiallycylindrical shape and is surrounded by a housing that is made up of aconverter receptacle 14, cast from aluminum, and an external annularprofile 16, which surrounds a device part used for active air cooling,which is sealed at the front side by a cover 18. Cover 18 is providedwith air passage openings 21, which are protected from rain by fins 20,while converter receptacle 14 is sealed by a supporting ring 17, a seal19, and a front plate 22, as is shown in FIG. 4. Behind cover 18, thereis situated a slotted disk 23 and, if necessary, an air filter.Converter receptacle 14 and external annular profile 16 have the sameouter diameter, and can be plugged into one another in the axialdirection at their connection point 24 and secured in this position bysuitable screw connections, as is shown in FIGS. 2 to 6.

As FIGS. 3 and 4 clearly show, board chamber 28, fashioned insideconverter receptacle 14, is completely separated from the transformerand cooling area 30, which in these Figures is connected at the left andis outwardly limited by external annular profile 16 and cover 18. Boardchamber 28 accommodates the electrical circuits of the converter device.Converter board 32 that is housed there, with power module, isencapsulated to form a unit and is exchangeable. A front wall ordividing wall 31, facing transformer and cooling area 30, of converterreceptacle 14 is prepared for the installation of an AC-operatedventilator or fan 34 whose air routing is indicated by arrows in FIG. 3and is described in more detail below.

Outer annular profile 16 (FIG. 6), centered with converter receptacle 14that was manufactured e.g. by an aluminum casting method, can beconnected through a tongue-and-groove design to a likewise annular basicbody profile 36 that outwardly limits a transformer chamber 38. A radialdistance is maintained from the inner surface of external annularprofile 16, so that an air inlet duct 40 (annular duct) is formed thatacts as a cooling air duct and that extends in the axial direction fromcover 18 up to the area between transformer chamber 38 and board chamber28 that acts as an air deflection 41 and that accommodates fan 34. Thetongue-groove connection is made up of integrally formed tongues 42 onthe inner side of external annular profile 16 and groove-type channels44, allocated to these tongues, on the outside of basic body profile 36.

In the direction towards cover 18, and in the direction towards airdeflection 41, transformer chamber 38, surrounded by basic body profile36, is closed respectively by an annular cover 46 or 47, which permitthe centering of a cooler profile 48 (FIG. 8). Cooler profile 48 limitstransformer chamber 38 with its external surface formed on an outer ring49, and is provided with large-surface fins 50 and 52, some of which arelarge in surface, on the inside of external ring 49. Large-surface fins52 are connected in one piece with an inner ring 54, which radiallyinwardly limits an air outlet duct 56 that runs from fan 34 to cover 18with passage openings 18. Strictly speaking, air outlet duct 56 is madeup of a large number of individual ducts, each of which is limited byouter ring 49 and inner ring 54 and is limited laterally by fins 52, ascan be seen particularly well in FIG. 8.

The chamber enclosed by inner ring 54 is closed at its side facing fan34 by a cover 58.

In transformer chamber 38 there is situated a transformer assembly madeof three encapsulated toroidal cores 60 a, 60 b, and 60 c. The isolatingtransformer having toroidal cores 60 a, 60 b, and 60 c is thus situatedcompletely, in annular fashion, between basic body profile 36 and coolerprofile 48. Cooling air flows past the isolating transformer, thusbringing about an effective cooling, both on the radial outer side viaair inlet duct 40 and also on the radial inner side via air outlet duct56.

Because the cooling air is also directed past separating wall 31, thiswall, which closes board chamber 28, is also cooled. The heat-producingdevices of the converter device on converter board 32, which arefastened on the rear side of separating wall 31, thus also experience aneffective cooling.

Through the use of aluminum extruded profiles, the housing of thefrequency converter according to the present invention can beconstructed very easily. In particular, it is easily possible, bymodifying the length of the extruded profiles, to modify the length andthus the size of the housing in order to adapt it to differentconstructive sizes of converter devices or isolating transformers, or inorder to realize different desired cooling configurations.

On the basis of the Figures, a preferred specific embodiment of thepresent invention has been explained in detail. Of course, within thescope of the present invention it is also possible to deviate from theconcrete embodiment thus described. Thus, for example, it isunproblematically conceivable to direct the cooling air stream in thedirection opposite to that shown in FIG. 3 and discussed above. Both thedirection and also the course of the cooling air stream can be varied asrequired. Depending on the construction, this can be carried out merelyby reversing the blowing direction of the fan.

In addition, it is possible to situate the fan at a different locationthan in the air deflection area. Thus, for example, it is conceivable tosituate the fan at the end of the cooling air ducts, so that in suctionoperation the cooling air is drawn exclusively through the frequencyconverter. Conversely, the fan can also be situated upstream from thecooling air ducts of the frequency converter.

1. A frequency converter, for construction site devices operated with anelectrical current having a higher frequency than line frequency, thefrequency converter comprising: a converter device for converting theelectrical current frequency; and a housing that surrounds the converterdevice, the housing comprising a converter receptacle that surrounds aboard chamber for the converter device, a housing segment that isconnected to the converter receptacle, that is isolated from theconverter receptacle that acts as a cooling area, inside which there aresituated cooling air ducts and a fan that is suitable for conveyingcooling air through the cooling air ducts, and in the cooling area, 1)an external, first annular profile, and 2) additional annular profilesare oriented to one another in relation to the axis of the first annularprofile in such a way that the annular profiles surround each other witha distance from one another, transverse to a main axial direction of thehousing, so as to form at least two annular chambers that act as coolingair ducts; wherein the annular profiles are situated inside the firstannular profile end with an axial spacing from the separating wall ofthe converter receptacle so as to form an air deflection area that actsas a cooling air duct, wherein the cooling area has a transformerchamber, adjacent to the cooling air ducts, for accomodating anisolating transformer for producing an output voltage that differs froma line voltage.
 2. A frequency converter, for construction site devicesoperated with an electrical current having a higher frequency than linefrequency, the frequency converter comprising: a converter device forconverting the electrical current frequency; and a housing thatsurrounds the converter device, the housing comprising a converterreceptacle that surrounds a board chamber for the converter device, ahousing segment that is connected to the converter receptacle, that isisolated from the converter receptacle that acts as a cooling area,inside which there are situated cooling air ducts and a fan that issuitable for conveying cooling air through the cooling air ducts, and inthe cooling area, 1) an external, first annular profile, and 2)additional annular profiles are oriented to one another in relation tothe axis of the first annular profile in such a way that the annularprofiles surround each other with a distance from one another,transverse to a main axial direction of the housing, so as to form atleast two annular chambers that act as cooling air ducts; wherein theannular profiles are situated inside the first annular profile end withan axial spacing from the separating wall of the converter receptacle soas to form an air deflection area that acts as a cooling air duct,wherein the fan is situated inside the first annular profile, coaxialthereto, in such a way that it is suited to draw a cooling air streaminto the fan via one of the annular chambers, to guide the cooling airstream past at least a part of the separating wall in the air deflectionarea, and to expel the cooling air stream via a different annularchamber according to a counterfiow principle, and wherein, adjacent tothe first annular profile, there is situated a second annular profilethat surrounds an annular transformer chamber that is limited inwardlyby a third annular profile.
 3. The frequency converter according toclaim 2, wherein, in order to form a heat sink, the third annularprofile is made up of an outer ring and an inner ring, cooling finsbeing situated in an area between the outer and inner rings that form awall of one of the annular chambers acting as cooling air ducts.
 4. Thefrequency converter according to claim 3, wherein a part of the coolingfins connects the outer ring and the inner ring to one another, andwherein between the cooling fins, fins are situated on the outer ringthat protrude radially inward.
 5. The frequency converter according toclaim 2, wherein the transformer chamber can be closed in the axialdirection by annular covers that extend between an outer limitation, bythe second annular profile, and an inner limitation, by the thirdannular profile, of the transformer chamber.
 6. The frequency converteraccording to claim 2, wherein the transformer chamber contains atoroidal core transformer assembly.
 7. The frequency converter accordingto claim 2, wherein the third annular profile is centered in relation tothe second annular profile, which is adjacent to the first annularprofile, by a cover that closes the transformer chamber.
 8. Thefrequency converter according to claim 2, wherein the fan is situatedsuch that it draws cooling air into the fan via the annular chamberadjacent to the first, outer annular profile, and conducts the coolingof air to the outside via the annular chamber enclosed by thetransformer chamber.